Cellular communication systems have generally operated using radio frequencies that are licensed by regulatory authorities. Increasing usage of cellular communication systems, however, has increased the demand for radio frequencies. To address this need, authorities in some countries have made certain unlicensed spectrums available for use by cellular communication systems. In the United States, for example, certain frequency bands in the range of 5.15 Gigahertz (GHz) to 5.825 GHz can be legally used without license by wireless carriers. Long-Term Evolution (LTE) systems that use unlicensed frequencies do so in accordance with standards and techniques that are referred to as LTE-Unlicensed (LTE-U) access or Licensed Assist Access (LAA).
The 5 GHz unlicensed bands are used by various types of devices. Significantly, the 5 GHz unlicensed bands are used by various types of Wi-Fi devices that communicate wirelessly in accordance with IEEE 802.11 standards and protocols. Wi-Fi devices are commonly used by both businesses and homes for various types of communications, and are frequently used to implement access points through which wireless devices such as personal computers and tablet computers can access the Internet and other networks. Accordingly, the unlicensed 5 GHz bands can often be relatively congested.
Because the use of the unlicensed bands is shared by multiple devices, cellular communication systems must take measures to avoid interfering with other users of the bands. Components of cellular communication systems are often configured so that they use channels of the unlicensed bands only during times when these channels are not otherwise in use, such as between transmissions of other devices. As a result, given a channel bandwidth, a cellular system may only be able to use a fraction or percentage of that bandwidth.
A communication session established by a cellular carrier can use channel aggregation, in which session communications are carried by multiple channels. These channels can be within a single band or in multiple bands. In some cellular systems, a session may use a primary link and one or more supplemental links. The primarily link is typically established through a channel of a licensed band. A supplemental link can be established through a channel of either a licensed or unlicensed band.